The present invention relates to a method for manufacturing ferrocenyl-1,3-butadiene. More particularly, the present invention relates to a method for manufacturing ferrocenyl-1,3-butadiene without heating or vacuum sublimation.
U.S. Pat. Nos. 3,739,004 and 3,843,426 disclose that ferrocenyl-1,3-butadiene is a starting material for manufacturing copolymer and homopolymer, which can be employed in applications such as the coating material for aerospace transportation to enhance resistance to photo degradation, ultraviolet rays and gamma rays. Ferrocenyl-1,3-butadiene also can be employed as an enhancement fuel in solid propellant. The fuel of the solid propellant comprises aluminum powder and ammonium perchlorate. Additionally, ferrocenyl-1,3-butadiene not only can be an enhancement fuel in solid propellant but also can decrease binder use.
U.S. Pat. No. 6,211,392B1 discloses a method of manufacturing ferrocenyl-1,3-butadiene, in which a ferrocenecarbonyl is reacted with an allyl halide in a polar aprotic solvent lacking a carbonyl group in the presence of samarium diiodide as a catalyst. The method of this U.S. patent has a relatively high yield; however, the catalyst used, samarium diiodide, is expensive and will undergo hydrolysis in air or moisture.
Several processes for preparing ferrocenyl-1,3-butadiene have been described in the U.S. Pat. No. 6,211,392B1, including the method disclosed in the U.S. Pat. No.3,739,004, the details of which are incorporated herein by reference.
There is still a need in the industry for developing an easier method for the preparation of ferrocenyl-1,3-butadiene.
The present invention provide a method for synthesizing ferrocenyl-1,3-butadiene having the following Formula III, which comprises: a) reacting ferrocenecarbonyl having the following Formula I with allyl halide having the following Formula II in an ether solvent and in the presence of magnesium as a catalyst; b) introducing a liquid portion of the resulting reaction mixture into a silica gel column; c) eluting the silica gel column with a solvent of low polarity; d) collecting the resulting eluate from the column; and e) evaporating the solvent from the eluate to a solid comprising ferrocenyl-1,3-butadiene: 
wherein R is hydrogen or C1-C4 alkyl; 
wherein X is halogen, and preferably X is bromine; 
wherein R is the same as above.
Preferably, the ether solvent is tetrahydrofuran or ethyl ether.
Preferably, said solvent of low polarity is n-hexane.
Preferably, said reaction in step a) is carried out for a period of 1-10 hours at room temperature.
Preferably, said liquid portion is kept in the silica gel column for a period of 1-48 hours in step b).
In the method of the present invention, the reaction mixture in step a) does not need to be heated under refluxing, and the catalyst used in a common alkaline earth metal.
A synthesis method for ferrocenyl-1,3-butadiene according to one of the preferred embodiments of the present invention can be represented by the following reaction formula: 
wherein Fc is ferrocenyl, and R is hydrogen or C1-C4 alkyl. Ferrocenecarbonyl (I) reacts with allyl bromide (II) in the presence of magnesium metal as a catalyst and in tetrahydrofuran (THF). The liquid portion of the reaction mixture is introduced into a silica gel column, and is kept in the silica gel column for a certain period of time such that the silica gel having a weak acidity dehydrates the reaction intermediate 1-ferrocenyl-3-buten-l-ol into ferrocenyl-1,3-butadiene (III) having a lower polarity. Next, n-hexane having a low polarity is used to desorb the product (III), and the eluate is collected. After removing the solvent by evaporation, a purified ferrocenyl-1,3-butadiene product is obtained. The silica gel used in the present invention is not limited and can be an arbitrary commercial silica gel. The invented method is simple to be operated and requires no refluxing or vacuuming. Moreover, the catalyst used is stable and is not expensive.
In the method for synthesizing ferrocenyl-1,3-butadiene (III), the amount of the allyl bromide (II) used is 0.1xcx9c100 (preferably 1.5) times of the mole number of the ferrocenecarbonyl (I) used. The amount of the magnesium metal used is 0.1xcx9c100 (preferably 3) times of the mole number of the ferrocenecarbonyl (I) used. The amount of THF used is 1xcx9c1000 L (preferably 15L) per mole of ferrocenecarbonyl (I) used.